The present invention relates to a semiconductor device and a manufacturing method for the semiconductor device.
At present, as a structure of an LDMOS (Laterally Diffused Metal Oxide Semiconductor) transistor for improving an off-state breakdown voltage, a structure described in US Patent Application Publication No. 2010/0314670 is known.
The LDMOS transistor described in US Patent Application Publication No. 2010/0314670 has a semiconductor substrate, an insulating film, a polycrystalline silicon film and a gate electrode. The semiconductor substrate has a first surface and a second surface. A trench which extends toward the second surface is formed in the first surface of the semiconductor substrate. The semiconductor substrate has an n-type source region which is arranged in the first surface, an n-type drain region which is arranged in the first surface separately from the source region, an n-type drift region which is arranged in the first surface so as to surround the drain region and a p-type channel region which is arranged in the first surface so as to be sandwiched between the drain region and the source region.
The insulating film is arranged on sidewalls and a bottom wall of the trench. The polycrystalline silicon film is arranged on the insulating film so as to fill the trench. The gate electrode faces the channel region while being insulated from the channel region.